Preheat the oven to 375 degrees. Prepare a large baking sheet by covering it with parchment paper or spraying with oil.
Mix all the ingredients in a large bowl and mash the beans well with a potato masher until mostly smooth.
Using a large scoop measure out 8 patties on the baking sheet. Flatten the tops with your hand or a spatula.
Bake for 20 minutes on one side. Then take out of the oven and flip the burgers over with a spatula and bake for 10 to 15 more minutes until firm.
Serve on a bun with mustard .